Method for manufacture of esters by transesterification

ABSTRACT

A method for the manufacture of an ester by transesterification allows the transesterification reaction to proceed within a short reaction time and under a pressure of the order of normal pressure. It was found that transesterification proceeds when a starting material ester and an alcohol are brought into contact with a catalyst comprising (A) an amorphous zirconium oxide and (B) an oxide of a Group II element, an oxide of a Group V element, and/or an oxide of a Group IV element other than zirconium and hafnium. In this method, it is preferred that the starting material ester in a liquid-phase state and the alcohol in a vapor-phase state be brought into contact with a solid acid catalyst comprising the above components (A) and (B), the starting material ester be an oil or fat, and the alcohol be methanol or ethanol. An oxide of titanium, silicon, germanium, or tin is the preferred oxide of the Group IV element other than zirconium and hafnium.

The present application is a national stage application ofPCT/JP04/09250, filed under 35 USC 371.

TECHNICAL FIELD

The present invention relates to a method for the manufacture of esterssuch as fatty acid esters from starting material esters such astriglycerides, diglycerides, and monoglycerides by transesterification.

BACKGROUND ART

Transesterification is used for the manufacture of fatty acid esters,for example, by using oils and fats which are esters of fatty acids andglycerin. Alkali catalysts such as caustic soda, zinc catalysts, andlipase can be used as catalysts. Furthermore, it was also suggested toconduct the reaction in a supercritical state, without the addition of acatalyst (Japanese Patent Publication Nos. 9-235573A, 7-197047A, and2000-143586A).

DISCLOSURE OF THE INVENTION

When an alkali catalyst such as caustic soda is used, the reaction timeis long and the catalyst has to be separated after the reaction.Furthermore, when the starting materials contain a large quantity offree fatty acids, pretreatment is required to remove them. Anotherproblem was that transesterification could not proceed due to asaponification reaction. When a zinc catalyst was used or when thereaction proceeded in a supercritical state, the reaction typically hadto be conducted under a pressure as high as 5 MPa to 8 MPa.

It is an object of the present invention to provide a method for themanufacture of esters by transesterification, this method allowing thetransesterification to proceed within a short reaction time and under apressure of the order of normal pressure.

The inventors have found that transesterification is promoted if astarting material ester and an alcohol are brought into contact with acatalyst comprising (A) an amorphous zirconium oxide and (B) an oxide ofGroup III element, an oxide of Group V element, and/or an oxide of GroupIV element other than zirconium and hafnium. In this method, it ispreferred that a starting material ester in a liquid-phase state and analcohol in a vapor-phase state be brought into contact with a solid acidcatalyst comprising the above components (A) and (B), the startingmaterial ester be an oil or fat, and the alcohol be methanol or ethanol.The content of amorphous zirconium oxide as the component (A) bepreferably 10 to 99 wt. %, more preferably 40 to 99 wt. %, based on thecatalyst weight. It is also preferred that an oxide of titanium,silicon, germanium, tin, etc. be used as the oxide of the Group IVelement other than zirconium and hafnium, which is mentioned as one ofthe component (B). Furthermore, when the component (B) is constituted byoxides of Group III and Group V elements, it is preferred that the totalcontent of the oxides of Group III and Group V elements be, calculatedas the elements, 0.5 wt. % or more based on the zirconium element weightand the content of amorphous zirconium oxide as the component (A) be 10to 99 wt. %, based on the catalyst weight. The crystallizationtemperature of the amorphous zirconium oxide is preferably 450° C. orhigher.

It is preferred that the oxide of the Group III element in the catalystbe aluminum oxide, the content thereof be, calculated as the element, 40to 1 wt. % based on the weight of zirconium element, the oxide of theGroup V element in the catalyst be phosphorus oxide, and the contentthereof be, calculated as the element, 8 to 0.8 wt. % based on theweight of zirconium element.

BEST MODE FOR CARRYING OUT THE INVENTION Starting Material Esters

Starting material esters used in the present invention may be anymaterials containing an ester compound as the main component, and theymay be polyesters. It is especially preferred that glyceride esters ofsaturated or unsaturated aliphatic carboxylic acids (carboxylic acidswith the number of carbon atoms of about 8-24) be used. Morespecifically, it is preferred that triglycerides that are called oilsand fats be used. Examples of such oils and fats include vegetable oilsand fats such as soybean oils, coconut oil, olive oil, arachis oil,cotton seed oil, sesame oil, palm oil, castor oil, etc., and animal oilsand fats such as beef tallow, lard, horse fat, whale oil, sardine oil,mackerel oil, etc. The starting material ester may contain 0 to 30 wt.%, more specifically 1 to 20 wt. % free fatty acid.

Alcohol

Alcohols containing 1 to 3 carbon atoms, in particular, methanol andethanol, are preferably used as the alcohol employed in accordance withthe present invention. Polyhydric alcohols may be also used.

Catalyst

The catalyst used in accordance with the present invention comprises anamorphous zirconium oxide as the main component, and the content ofzirconium oxide is 10 to 99 wt. %, preferably 40 to 99 wt. %, even morepreferably 80 to 98 wt. %, in case of a catalyst comprising the oxidesof a Group III element and/or Group V element as the component (B).Furthermore, the content of zirconium oxide is 10 to 95 wt. %,preferably 40 to 80 wt. %, in the case of a catalyst comprising theoxide of the Group IV element other than zirconium and hafnium, as oneof the component (B). Here, zirconium oxide also includes the hydratedoxide state. The term “amorphous” means that substantially nodiffraction peaks are observed in X-ray diffraction (XRD). Morespecifically, the intensity of diffraction peaks is less than thedetection limit, or only peaks with an intensity of 2 or less aredetected, where the diffraction intensity of crystalline zirconium oxideis taken as 100.

The catalyst employed in accordance with the present invention cancontain an oxide of a Group IV element other than zirconium and hafniumas the component (B), and titanium oxide and silicon oxide can be usedas this oxide. When titanium oxide is used, the content thereof in thecatalyst is 5 to 90 wt. %, preferably 10 to 60 wt. %, and when siliconoxide is used, the content thereof is 1 to 20 wt. %, preferably 2 to 10wt. %. The total content of the elements of Groups I-II and GroupsVI-VII as the catalyst component is 1 wt. % or less, and it isespecially preferred that the catalyst substantially not contain theseelements, with the content thereof 0.2 wt. % or less. If necessary, aGroup VIII element may be added in an amount of 0.1 to 5 parts by weightper 100 parts by weight of the catalyst. In addition, boron oxide,aluminum oxide, yttrium oxide, and lanthanoide element oxides, etc. maybe used as a binder.

Further, the oxides of Group III and Group V elements are also effectiveas the component (B) of the catalyst used in accordance with the presentinvention. The oxides of those elements are contained at a content of0.5 wt. % or more, calculated as their elements, based on the zirconiumelement weight.

Oxides of aluminum, gallium, indium, thallium, and yttrium can be usedas the oxide of the Group III element. The content of the oxide of theGroup III element is preferably not more than ⅓ of zirconium content, asthe weight ratio of the elements. When aluminum oxide is used, thecontent thereof, is, calculated as the element, 40 to 1 wt. %,preferably 30 to 1 wt. %, even more preferably 25 to 1 wt. %, based onthe zirconium element weight.

The Group III element oxide is preferably contained in the catalyst inthe state such that it is exposed together with zirconium oxide on thesurface of the catalyst and the crystal growth of zirconium oxide isinhibited by the Group III element oxide. As a result, as describedhereinbelow, the crystallization temperature of zirconium oxidepreferably becomes 450° C. or higher. If the content of the Group IIIelement oxide is too low, the crystal growth of zirconium oxide isenhanced, and if this content is too high, most of the surface of thezirconium oxide is covered with the Group III element oxide, therebydegrading the catalytic activity. The oxide of the Group IV elementother than zirconium and hafnium is assumed to act on the zirconiumoxide as mentioned about the Group III element oxide.

Oxides of phosphorus, arsenic, antimony, bismuth, etc., can be used asthe Group V element oxide. The content thereof is preferably not morethan ⅕ of the zirconium element, as an element weight ratio. Whenphosphorus oxide is used, the content thereof is, calculated as theelement, 8 to 0.8 wt. %, in particular, 6 to 1 wt. %, based on thezirconium element weight.

As for the contained Group V element oxide, it is preferred thatphosphorus oxide cover the catalyst surface with a monomolecular layer.The catalyst may contain a combination of two or more of the Group IIIelement oxide, the Group IV element oxide and the Group V element oxide.In any case, the crystal growth of zirconium oxide is suppressed, andthe crystallization temperature of zirconium oxide is preferably 450° C.or higher, more preferably 500° C. or higher, even more preferably 550°C. or higher. Usually it is 900° C. or less. The crystallizationtemperature can be measured as a peak temperature of the exothermic peakat which no changes in weight are observed in thethermogravimetric-differential thermal analysis (TG-DTA) conducted byheating from room temperature.

The total content of elements other than the components (A) and (B)mentioned as the catalyst components and Group VIII elements ispreferably 1 wt. % or less, more preferably such elements besubstantially absent, that is, they are present at 0.2 wt. % or less.Furthermore, if necessary, a Group VIII element may be added in anamount of 0.1 to 5 parts by weight per 100 parts by weight of thecatalyst.

In the catalyst employed in accordance with the present invention, themean particle size is 2 to 200 μm, preferably 4 to 40 μm, the specificsurface area is 100 to 400 m²/g, preferably 150 to 400 m²/g, and thecentral pore diameter D50 is 2 to 10 nm, preferably 2 to 8 nm. Thespecific surface area and central pore diameter can be measured by anitrogen adsorption and desorption method. Further, when the catalyst isshaped, alumina having γ, η or other crystallinity may be used as abinder.

Composite oxide powders comprising the components (A) and (B)constituting the catalyst used in accordance with the present inventionare generally available and can be purchased, for example, from DaiichiKigenso Kagaku Kogyo Co., Ltd. Further, composite oxide powderscomprising titanium oxide and an oxide of a Group IV element other thantitanium, for example, silicon or tin, can be also used as the compositeoxide powder to prepare the catalyst for transesterification.

Transesterification

The reaction temperature is such that the starting material ester is ina liquid-phase state and the alcohol is in a vapor-phase state. Morespecifically, the reaction temperature is 100° C. or higher, preferably150 to 350° C. No limitation is placed on the reaction pressure.Although the reaction can proceed sufficiently even under an atmosphericpressure of about 0.05 to 0.2 MPa, the reaction pressure is preferably0.1 to 4 MPa, more preferably 0.1 to 3 MPa. The reaction may be alsoconducted in the so-called supercritical state. No limitation is placedon the reaction time. However, in a batch mode the reaction time isabout 0.1 to 1 hour, and in a flow-through mode the product can besufficiently obtained at a WHSV (Weight-Hourly Space Velocity) of about0.5 to 5 (/hour). The ester manufactured by the present reaction ispreferably obtained in the form of a liquid phase to facilitateseparation from the catalyst. The reaction can be conducted in batchmode or a flow-through mode. The catalyst in accordance with the presentinvention is preferably used as a fixed bed. In this case, it is notcontained in the product and can be separated and recovered.

EXAMPLES

The present invention will be described below in greater detail based onexamples thereof.

Example 1

The properties of the composite oxides manufactured by Daiichi KigensoKagaku Kogyo Co., Ltd., which were used as the catalysts, are presentedin Table 1. A zirconium oxide powder (reagent manufactured by MEL Co.,Ltd. (Great Britain)) fired in air for 2 hours at a temperature of 400°C. (Z-1) was used for comparison. The presence of X-ray diffractionpeaks was determined by whether or not a diffraction peak exceeding thedetection limit was detected at a scanning speed of 4°/min and ascanning width of 0.02° in RAD-1C (CuKα, tube voltage 30 kV, tubecurrent 20 mA) manufactured by Rigaku Denshi Co., Ltd. When there was nopeak, exceeding the detection limit or when only a peak of 2 or less waspresent (the peak intensity of the fired zirconium oxide powder (Z-1)was taken as 100), the peak was assumed to be absent.

Each of those oxides was used as a catalyst, a fixed-bed flow reactorwith a length in the up-down direction of 50 cm and an inner diameter of1 cm was filled with 4 g of the catalyst, soybean oil (manufactured byKanto Kagaku Co., Ltd.) as a starting material ester and methanol as analcohol were introduced from the top end, and a conversion rate of thesoybean oil in the outlet at the lower end was measured by gaschromatography at a point of time of 4 hours or 20 hours after the testwas started.

The reaction conditions were as follows:

reaction pressure: atmospheric pressure,

reaction temperature: 200° C.,

starting material flow rate of soybean oil: 3.0 g/h,

starting material flow rate of methanol: 4.4 g/h, and

WHSV: 1.85/h.

The test results relating to transesterification are shown in Table 1.When the composite oxides of test examples 1 to 6 were used ascatalysts, the conversion rate was high. In particular, it is clear thatan even higher conversion rate was obtained in test examples 2 to 6which were the examples using a composite oxide comprising an amorphouszirconium oxide as a catalyst.

TABLE 1 Test example 1 2 3 4 5 6 7 Oxide number I-1454 D-1564 I-1455D-1514 D-1515 I-1457 Z-1 Composition (wt. %) ZrO₂ 93.08 82.10 70.2250.02 14.12 95.73 100 TiO₂ 6.92 17.90 29.78 49.98 85.88 0.0 0.0 SiO₂ 0.00.0 0.0 0.0 0.0 4.27 0.0 Mean particle 3.9 4.0 5.82 9.21 112.7 13.1 —size(μm) Specific surface 118.3 201.7 172.7 173.8 115.0 387.9 87area(m²/g) Central pore 9.34 5.62 5.00 7.17 8.11 2.58 5.6 diameter (nm)X-ray diffraction peak ZrO₂ Yes No No No No No Yes TiO₂ No No Yes YesYes No No SiO₂ No No No No No No No Conversion rate After 4 hours 33%55% 51% 53% 40% 54% 14% After 20 hours 28% 48% 43% 45% 36% 56% 10%

Example 2

The properties of the composite oxides manufactured by Daiichi KigensoKagaku Kogyo Co., Ltd., which were used as the catalysts, are presentedin Table 2. A zirconium oxide powder (reagent manufactured by MEL Co.,Ltd. (Great Britain)) fired in air for 2 hours at a temperature of 400°C. (Z-1) was used for comparison. The presence of X-ray diffractionpeaks was determined by whether or not a diffraction peak exceeding thedetection limit was detected at a scanning speed of 4°/min and ascanning width of 0.02° in RAD-1C (CuKα, tube voltage 30 kV, tubecurrent 20 mA) manufactured by Rigaku Denshi Co., Ltd. When there was nopeak exceeding the detection limit or when only a peak of 2 or less waspresent (the peak intensity of the fired zirconium oxide powder (Z-1)was taken as 100), the peak was assumed to be absent. Thethermogravimetric-differential thermal analysis (TG-DTA) for measuringthe crystallization temperature was conducted with a device manufacturedby Mac-Science Co., Ltd. (TG-DTA2000S) by raising the temperature fromroom temperature to 1500° C. at a rate of 20° C./min under an air flow.

Each of those oxides were used as a catalyst, a fixed-bed flow reactorwith a length in the up-down direction of 50 cm and an inner diameter of1 cm was filled with 4 g of the catalyst, soybean oil (manufactured byKanto Kagaku Co., Ltd.) as a starting material ester and methanol as analcohol were introduced from the top end, and the conversion rate of thesoybean oil in the outlet at the lower end was measured by gaschromatography at a point of time of 20 hours after the test wasstarted.

The reaction conditions were as follows:

reaction pressure: atmospheric pressure,

reaction temperature: 200° C. or 250° C.,

starting material flow rate of soybean oil: 3.0 g/h,

starting material flow rate of methanol: 4.4 g/h, and

WHSV: 1.85/h.

The test results relating to transesterification are shown in Table 2.It is clear that a high conversion rate is obtained in Test Examples 8to 10, which are the examples using a composite oxide comprising anamorphous zirconium oxide as a composite oxide catalyst.

TABLE 2 Test examples 8 9 10 7 Composition Oxide number (wt. %) K-1407E-1565 E-1565 Z-1 ZrO₂ 91.3 95.8 95.8 100 PO₄ 8.7 0.0 0.0 0.0 Al₂O₃ 0.04.2 4.2 0.0 Mean particle 22.5 4.9 4.9 — size (μm) Specific 131 197 19787 surface area (m²/g) Central pore — — — 5.6 diameter (nm) X-ray No NoNo Yes diffraction peak Crystallization 745° C. 626° C. 626° C. alreadytemperature crystal- lized Reaction 250 200 250 200 temperature (° C.)Conversion rate 83% 59% 80% 10% (After 20 hours)

Example 3

The properties of the composite oxides manufactured by Daiichi KigensoKagaku Kogyo Co., Ltd., which were used as the catalysts, are presentedin Table 3. A zirconium oxide powder (reagent manufactured by MEL Co.,Ltd. (Great Britain)) fired in air for 2 hours at a temperature of 400°C. (Z-1) was used for comparison. The presence of X-ray diffractionpeaks was determined by whether or not a diffraction peak exceeding thedetection limit was detected at a scanning speed of 4°/min and ascanning width of 0.02° in RAD-1C (CuKα, tube voltage 30 kV, tubecurrent 20 mA) manufactured by Rigaku Denshi Co., Ltd. When there was nopeak exceeding the detection limit or when only a peak of 2 or less waspresent (the peak intensity of the fired zirconium oxide powder (Z-1)was taken as 100), the peak was assumed to be absent. Thethermogravimetric-differential thermal analysis (TG-DTA) for measuringthe crystallization temperature was conducted with a device manufacturedby Mac-Science Co., Ltd. (TG-DTA2000S) by raising the temperature fromroom temperature to 1500° C. at a rate of 20° C./min under an air flow.

Each of those oxides was used as a catalyst, a fixed-bed flow reactorwith a length in the up-down direction of 50 cm and an inner diameter of1 cm was filled with 4 g of the catalyst, soybean oil (manufactured byKanto Kagaku Co., Ltd.) as a starting material ester and methanol as analcohol were introduced from the top end, and a conversion rate of thesoybean oil in the outlet at the lower end was measured by gaschromatography at a point of time of 20 to 48 hours after the test wasstarted.

The reaction conditions were as follows:

-   -   reaction pressure: atmospheric pressure, 1.0 MPa, 2.0 MPa or 3        MPa    -   reaction temperature: 200° C. to 250° C.,    -   starting material flow rate of soybean oil: 3.0 g/h,    -   starting material flow rate of methanol: 4.4 g/h, and    -   WHSV: 1.85/h.

The test results relating to transesterification are shown in Table 3.It is clear that a high conversion rate is obtained in Test Examples 11to 23, which are the examples using a composite oxide comprising anamorphous zirconium oxide as a composite oxide catalyst. Among TestExamples 18 to 23, Test Examples 18 and 22 containing a somewhat low orhigh titanium oxide content showed a slightly low conversion rate ascompared with other test samples.

TABLE 3 Test example 11 12 13 14 15 16 17 Oxide number E-1565 E-1565K-1570 K-1570 K-1570 K-1570 K-1570 Composition (wt. %) ZrO₂ 95.8 95.895.0 95.0 95.0 95.0 95.0 PO₄ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Al₂O₃ 4.2 4.25.0 5.0 5.0 5.0 5.0 TiO₂ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 SiO₂ 0.0 0.0 0.00.0 0.0 0.0 0.0 Mean particle 4.9 4.9 160.7 160.7 160.7 160.7 160.7 size(μm) Specific surface 197 197 179 179 179 179 179 area (m²/g) Centralpore 3.9 3.9 4.3 4.3 4.3 4.3 4.3 diameter (nm) X-ray diffraction peakZrO₂ No No No No No No No PO₄ No No No No No No No Al₂O₃ No No No No NoNo No TiO₂ No No No No No No No SiO₂ No No No No No No NoCrystallization 626 626 642 642 642 642 642 temperature(° C.) Reactiontemperature 200 250 250 250 250 230 210 Reaction Pressure Atmosphericpressure 1.0 2.0 3.0 3.0 3.0 (MPa) Conversion rate (%) 59(20 h) 80(20 h)97(29 h) 98(25 h) 98(22 h) 99(22 h) 93(46 h) (reaction time) Testexample 18 19 20 21 22 23 7 Oxide number I-1454 D-1564 D-1455 D-1514D-1515 I-1457 Z-1 Composition (wt. %) ZrO₂ 93.1 82.1 70.2 50.0 14.1 95.7100.0 PO₄ 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Al₂O₃ 0.0 0.0 0.0 0.0 0.0 0.0 0.0TiO₂ 6.9 17.9 29.8 50.0 85.9 0.0 0.0 SiO₂ 0.0 0.0 0.0 0.0 0.0 4.3 0.0Mean particle 3.9 4.0 5.8 9.2 112.7 13.1 — size (μm) Specific surface118 202 173 174 115 388 87 area (m²/g) Central pore 9.3 5.6 5.0 7.2 8.12.6 5.6 diameter (nm) X-ray diffraction peak ZrO₂ Yes No No No No No YesPO₄ No No No No No No No Al₂O₃ No No No No No No No TiO₂ No No Yes YesYes No No SiO₂ No No No No No No No Crystallization 759 605 576 600 725559 Already temperature(° C.) crystal- lized Reaction temperature 200200 200 200 200 200 200 Reaction Pressure Atmospheric pressure (MPa)Conversion rate (%) 28(20 h) 48(20 h) 43(20 h) 45(20 h) 36(20 h) 56(20h) 10(20 h) (reaction time)

INDUSTRIAL APPLICABILITY

In accordance with the present invention, the transesterificationreaction can be conducted within a short time under a pressure of theorder of normal pressure. Furthermore, the product and catalyst can beeasily separated. Therefore, the target ester can be produced with goodefficiency.

1. A method for the manufacture of an ester by transesterificationcomprising the step of bringing a starting material ester in a liquidphase state and an alcohol in a vapor phase state into contact with anamorphous solid acid catalyst consisting of (A) an amorphous zirconiumoxide and (B) aluminum oxide, wherein the content of the aluminum oxideis, calculated as the element, 25 to 1 wt. % based on the zirconiumelement weight.
 2. The method according to claim 1, wherein the startingmaterial ester is an oil or fat and the alcohol is methanol or ethanol.3. The method according to claim 1, wherein the starting material esteris a glyceride ester of a saturated or unsaturated aliphatic carboxylicacid having from 8-24 carbon atoms.
 4. A method for the manufacture ofan ester by transesterification comprising the step of bringing astarting material ester in a liquid phase state and an alcohol in avapor phase state into contact with an amorphous solid acid catalystconsisting of (A) an amorphous zirconium oxide and (B) phosphorus oxide,wherein the content of the phosphorus oxide is, calculated as theelement, 6 to 1 wt. % based on the zirconium element weight.
 5. Themethod according to claim 4, wherein the starting material ester is anoil or fat, and the alcohol is methanol or ethanol.
 6. The methodaccording to claim 4, wherein the starting material ester is a glycerideester of a saturated or unsaturated aliphatic carboxylic acid havingfrom 8-24 carbon atoms.
 7. A method for the manufacture of an ester bytransesterification comprising the step of bringing a starting materialester in a liquid phase state and an alcohol in a vapor phase state intocontact with an amorphous solid acid catalyst consisting of (A) anamorphous zirconium oxide and (B) titanium oxide, wherein the content ofthe amorphous zirconium oxide in the catalyst is 40 to 90 wt. % and thecontent of the titanium oxide is 60 to 10 wt. % in the catalyst.
 8. Themethod according to claim 7, wherein the starting material ester is anoil or fat, and the alcohol is methanol or ethanol.
 9. The methodaccording to claim 7, wherein the starting material ester is a glycerideester of a saturated or unsaturated aliphatic carboxylic acid havingfrom 8-24 carbon atoms.